1. Field of the Invention
The present invention relates to a fastening device for a polishing paper cloth, which is to be attached to and detached from a polishing base plate of a portable polishing machine and on which surface the polishing paper cloth is mounted. Particularly, it relates to a fastening device for a polishing paper cloth which is applicable in a portable polishing machine of such a type that the polishing is carried out at a front end portion of its polishing base plate.
2. Description of the Related Art
Conventionally, a portable polishing machine has been used on many occasions so as to deal with various abrasive operations. One example of this portable polishing machine comprises a main body with a handle grip and has a configuration similar to that of an iron for household use, from which the base plate is detachable. An attaching portion of the base plate with respect to the polishing machine main body may be connected to an oscillation source, or alternatively the whole polishing operation may be performed manually. On a surface of a front end portion of the base plate, a detachment portion for a fastening device, which serves to detachably support a fastening device to which a male member of a surface fastener is fixed, is integrally formed.
One example of a fastening device for a polishing paper cloth to be used for this kind of a manual polishing machine is disclosed in Japanese Patent Application Laid-Open No. 2000-176818. The fastening device for a polishing paper cloth as disclosed in this publication is a molded product made of synthetic resin such as polyester elastomer resin and various hard rubbers. The fastening device of the polishing paper cloth comprises an attachment portion which is attachable to and detachable from a base plate of the polishing machine and a main body for winding and fastening the polishing paper cloth thereon. On the fastening device main body, a plurality of surface-fastener engaging element rows, which are arranged along a winding direction of the polishing paper cloth, are integrally formed so that it forms an engaging surface. The polishing paper cloth is fixed to the engaging surface by engaging a pile member (a female surface fastener) formed on a rear surface of the polishing paper cloth.
The attachment portion of the fastening device has a long and narrow cubic shape having a substantially trapezoidal cross section. The foregoing fastening device main body is integrally connected to a bottom surface of the attachment portion and it is comprised of a horseshoe-like body having such a cross section that is enclosed by a circumference of not less than a half circle and tangent lines contacting on the same circumference. From front and rear end surfaces of the fastening device main body up to a substantially central portion thereof, cavity portions, which are blind and have centers at a central line of the half circle cross section, are formed in the longitudinal direction. This cavity portions secure the flexibility by facilitating elastic deformation of the fastening device, which is made of hard resin so that it is necessary to provide it with some flexibility at least in the vicinity of the front and rear of the fastening device upon polishing.
In the meantime, in the polishing operation, the portable polishing machine carries out the operation by attaching the fastening device to which the polishing paper cloth is winded to be integrally engaged therewith, strongly pressing the main body portion of the fastening device to a surface of a work piece to be polished and then operating it along an exterior shape of the work piece. At that time, extremely strong oscillation acts on the fastening device due to the polishing machine in many directions. Therefore, although the oscillation of the polishing machine is transmitted to the hand, the arm and the like of an operator through the fastening device, the operator is obliged to strongly press the fastening device on the surface of the work piece against these oscillation. Thus, the operator gets more and more physically tired. Further, in the long run, the operator is given to suffering from a disease such as an inflammation or the like on his or her hand, arm and the like for a long term.
In general, if the fastening device is made of a material having flexibility, it is possible to suppress a reaction applied to the operator by absorbing the oscillation. However, the fastening device, which is disclosed in the above described Japanese Patent Application Laid-Open, is molded of synthetic resin having less elasticity such as polyester elastomer resin and various hard rubbers, so that it is difficult to sufficiently absorb the oscillation.
Therefore, according to the above described prior art, the fastening device is made so as to be easily deformed elastically by forming cavity portions in an interior of the fastening device main body around which the polishing paper cloth is to be winded and with which the polishing paper cloth is to be engaged, so that it is possible to secure the flexibility of the fastening device. However, the cavity portions are formed in the longitudinal direction of the fastening device as described above so that they positively can allow the elastic deformation in the front and rear directions of the fastening device main body by their structures, they can hardly allow the elastic deformation in the longitudinal direction of the fastening device main body. Therefore, depending on the material to be used for the fastening device, the flexibility is not sufficient only with these cavity portions, so that it becomes difficult to suppress the reaction acting on the operator by the oscillation of the polishing machine generated upon polishing.
Furthermore, in the polishing operation, the extremely large force acts on both of the fastening device main body and the polishing paper cloth in many directions as described above. Therefore, friction heat is generated not only when the polishing paper cloth and the work piece to be polished by this polishing paper cloth are in friction with each other but also when the fastening device main body and the polishing paper cloth are in friction with each other. This friction heat to be generated upon the polishing is transmitted to the fastening device main body through a portion where the fastening device main body and the polishing paper cloth are in friction with each other, so that the fastening device main body melts by this large amount of friction heat to be deformed into an irregular shape.
Still further, according to the above described prior art, the fastening device main body has a plurality of surface-fastener engaging element rows which are integrally formed on a portion thereof directly serving the polishing so as to form an engaging surface. In this case, an non-engagement area, which has no engaging elements, is formed between the engaging element rows of the surface fastener. When the polishing operation is not carried out, a rear surface of the polishing paper cloth is engage with the engaging surface locally in such a manner that it is detached from the non-engagement area of the fastening device main body. Therefore, the polishing paper cloth does not positively is not in contact with the non-engagement area of the fastening device main body.
However, in the polishing operation, if the polishing operation is carried out by strongly pressing the fastening device to the work piece to be polished and operating it along the exterior shape of this work piece, the non-engagement area of the fastening device main body and the rear surface of the polishing paper cloth necessarily contact with each other by the pressing force. As a result, a gap between the fastening device main body and the rear surface of the polishing paper cloth is closed so as to shut off the outside air and block the ventilation, so that the heat radiation from the rear surface of the fastening device and the polishing paper cloth to the exterior becomes insufficient.
Still further, if the polishing waste or the like generated during the polishing operation intrude in a gap between the front surface of the fastening device main body and the rear surface of the polishing paper cloth from a longitudinal side edge portion of the fastening device main body to be accumulated without being discharged to the outside, the non-engagement area between the plurality of surface-fastener engaging element rows, which are formed on the engaging surface of the fastening device main body, gets clogged, so that the engagement of the fastening device main body and the polishing paper cloth is obstructed and the engagement force of the fastening device main body is decreased. As a result, the polishing paper cloth gets stripped off from the fastening device main body. Furthermore, if the polishing waste or the like intrudes in the gap between the front surface of the fastening device main body and the rear surface of the polishing paper cloth, both of the fastening device main body and the polishing paper cloth are rubbed with each other by a large frictional force due to the polishing waste or the like. Then, this frictional force generates heat, so that the fastening device main body is apt to melt and it is deformed into an irregular shape in a short period.
The present invention has been made taking the above conventional problems into consideration. Specifically, an object of the invention is to provide a flexibility to a fastening device main body of a fastening device, which is given to being easily deformed in many directions, as well as to provide a fastening device for a polishing paper cloth of a polishing machine which enables to prevent the deformation by heating and prevent clogging of the fastening device due to the polishing waste or the like generated in the polishing operation, so that it is possible to maintain a holding power of the polishing paper cloth with respect to the fastening device main body for a long term.
A basic feature of the present invention is in a synthetic-resin-made fastening device for a polishing paper cloth comprising, on a fastening device main body thereof, an attaching portion capable of being detached from and attached to a base plate of a polishing machine; and an engaging surface for winding the polishing paper cloth thereon to engage therewith, wherein the fastening device main body has a plurality of concave grooves on a surface thereof.
In this case, it is possible to apply common synthetic resins, which have been conventionally used, to the fastening device for a polishing paper cloth according to the present invention. As the material of this fastening device, for example, various thermoplastic elastomer resins and a synthetic rubber, which are excellent in heat resistance, weather resistance, metallic contact deterioration resistance and formability, can be applied.
On the engaging surface of the fastening device main body to be attached to the base plate of a polishing machine, for example, a plurality of surface-fastener engaging elements are integrally molded. Then, the polishing paper cloth is engaged with these surface fastener engaging elements to be united thereto, so that the polishing operation can be carried out. In this case, very large oscillation from the polishing machine acts in many directions and is transmitted to the hand, the arm or the like of the operator. Therefore, the reaction to act on the operator becomes very large. According to the present invention, a plurality of concave grooves are formed in an non-engagement area, which is located on a front surface of the fastening device main body and in which no surface-fastener engaging elements exist, and flexibility is given to the fastening device main body, which allows the fastening device to be easily deformed in many directions. As a result, the reaction to the operator due to the oscillation of the polishing machine generated in the polishing operation is effectively decreased.
It is preferable that the concave grooves are continuous in a winding direction of the polishing paper cloth.
In general, in the polishing operation according to the polishing paper cloth, the engaging surface and the rear surface of the polishing paper cloth, and the front surface of the polishing paper cloth and a work piece are repeatedly rubbed with each other, so that friction heat is generated, which make the temperature of the polished surface very high, and this heat is transmitted to the fastening device main body. As a result, the fastening device main body itself also reaches a high temperature. It is necessary that each of the concave grooves, which are continuous in the direction of the winding of the polishing paper cloth, has a width and a depth to an extent that they do not contact the polishing paper cloth even during the polishing. Owing to such a shape of the concave groove, the outside air can be flown through the concave grooves even during the polishing, so that it is possible to effectively discharge a large amount of friction heat, which is generated due to the repetition of the rubbing, to the outside and to secure a cooling function for improving the discharge efficiency of the friction heat generated in the polishing.
Further, the concave groove also serves as a chip pocket for facilitating the discharge of the polishing waste or the like of the polishing paper cloth and the work piece. A part of the polishing waste or the like, which is generated in polishing, is efficiently discharged to the outside through the continuing concave grooves by the oscillation of the polishing machine. Accordingly, it is possible to prevent clogging due to adhesion of minute polishing waste and any damage of a surface to be processed during the polishing, as well as it is possible to maintain a good engagement force of the polishing paper cloth with respect to the engaging surface of the fastening device main body for a long term.
Further, as described above, since a part of the polishing waste by the polishing operation easily can easily intrudes in the concave grooves and at the same time and it is efficiently discharged to the outside by the oscillation of the polishing machine, an increase of the friction heat, which is to be generated when the engaging surface s of the fastening device main body and the rear surfaces of the polishing paper cloth or the like are rubbed with each other through the polishing waste with a large friction force, can be suppressed to the utmost. As a result, it becomes possible to prevent the deformation of the fastening device main body due to the large amount of friction heat, so that the polishing with respect to the work piece can be carried out smoothly.
Furthermore, it is preferable that other than the concave grooves, the fastening device main body has another concave groove on a lower surface thereof.
Normally, at the time of the polishing operation, the fastening device main body is pressed to a surface of the work piece as strong as possible and operated along the exterior shape of the work piece. Therefore, it is the lower surface of the fastening device main body that is pressed most strongly on the surface of the work piece during the polishing operation. Thus, concave groove other than the above-described concave grooves is further formed at least on a lower surface of the fastening device main body that is most affected by the polishing. This other concave groove, for example, communicate with the concave grooves continuous in the winding direction of the polishing paper cloth, so that it provides flexibility to the fastening device main body itself, as well as it allows a part of the minute polishing waste or the like generating in polishing to easily intrude in the lower surface of the fastening device main body. Further, it has a discharging function to allow the minute polishing waste or the like to be smoothly circulated upwardly from the lower surface of the fastening device main body by the oscillation of the polishing machine and to be discharged to the outside. Therefore, the fastening device main body prevents the clogging due to the adhesion of the minute polishing waste and the friction heat or the like during the polishing operation from being generated.
Still further, it is preferable that the concave groove formed on the lower surface of the fastening device main body is continuously elongated over opposite side surfaces of the fastening device main body.
The concave groove, which is continuously elongated over the opposite side surfaces of the fastening device main body, is formed on the lower surface of the fastening device main body, which is most affected by the polishing and easily reaches to a high temperature. Owing to this concave groove, the discharge ratio and the cooling efficiency of the polishing waste are improved, and the clogging due to the adhesion of the minute polishing waste can be efficiently prevented. At the same time, the fastening device main body is not subject to deformation due to the friction heat during the polishing. As a result, it is possible to secure a required engagement force with respect to the polishing paper cloth even against the large force applied in many directions, as well as to improve the polishing efficiency. Thus, it is possible to perform the polishing with a high degree of accuracy for a long term.
It is preferable that the fastening device main body has a cavity portion opening at opposite end surfaces in a longitudinal direction thereof and that a thickness between the cavity portion and the engaging surface is substantially equal in the winding direction of the polishing paper cloth.
In the case that a constituent material of the fastening device main body is a hard synthetic resin or a hard rubber, the polishing paper cloth lineally acts on a surface to be polished during the polishing, which makes the polishing efficiency decreases. Therefore, according to the present invention, the thickness between the cavity portion and the engaging surface is formed to be substantially equal in the winding direction of the polishing paper cloth, so that the fastening device main body is capable of obtaining easy and uniform elastic deformation at any position on its surface. Hereby, an acting area of the polishing paper cloth with respect to the surface to be polished is increased, so that the polishing efficiency is improved. The degree of the elasticity can be changed by adjusting the size of the cavity portion.
In addition to the existence of the cavity portion, because the above described concave groove is formed, even if the large outer force acts on the fastening device main body in many directions, the fastening device main body can be easily deformed so that it is possible to secure the entire flexibility of the fastening device main body and to keep suppressing the reaction to be applied to the operator by the oscillation of the polishing machine generated during the polishing.
It is preferable that the cavity portion is partitioned at a center portion in the longitudinal direction of thereof by a vertical wall.
Since the fastening device main body is strongly pressed against the surface be polished in many directions during the polishing, the fastening device main body easily reaches a high temperature. Therefore, the fastening device easily changes its elastic deformation to a plastic deformation only with a mere cavity portion being formed on the fastening device main body, or it may be easily worn out, so that the fastening device main body can become flat. Particularly, since the above described worn-out is quite large at the center portion of the fastening device main body, it is preferable to secure rigidity at the center portion of the longitudinal direction of the fastening device main body while keeping the elasticity at its end portions, as well as to increase the strength, by partitioning the center portion of the longitudinal direction of the cavity portion with a vertical wall, as in the present invention. Due to this partition, the strength of the fastening device main body is appropriately increased, so that, even if large external force acting in many directions is applied, it is possible to maintain the durability of the polishing capability while keeping a required shape.
It is preferable that an interior of the cavity portion is further partitioned by a horizontal wall.
Said cavity portion is formed with the above described vertical wall at its center portion in the longitudinal direction, and it is further formed with a horizontal wall on a horizontal plane along a center line of the cavity portion. In other words, the inner cavity is divided into four chambers, i.e., upper, lower, right and left chambers by the partition walls forming a cross shape, in a side view of the fastening device. In the polishing, because the fastening device is strongly pressed so that it is easily deformed in many directions, it is necessary to appropriately increase the strength of the fastening device main body. Particularly, the above described horizontal wall provides appropriate elasticity to the fastening device main body while restricting the deformation of thereof in a direction orthogonal to a pressing direction. Therefore, it is possible to keep a required shape and to secure the polishing capability in cooperation with the vertical wall.